Characteristics of two compost formulas to valorize organic matter in Casamance (Senegal)

Abstract

Two different composting formulations F1 and F2 were studied at the station using different organic matter sources. F1 is made from rice straw and ground shells. F2 is composed of Andropogon gayanus K, phosphogypsum and urea. Temperature, humidity and pH were monitored during the composting process. Phytotoxicity tests were performed on rice using different doses of F1 and F2 composts to evaluate their maturity at 40 days and 50 days after incubation (DAI). The results showed that mean temperatures at the beginning of incubation were 49° C for (F1) and 41° C for (F2) and 31°C (F1) and 33°C (F2) at the 50th day after incubation (DAI). From the 28th DAI the average temperatures were similar for F1 (35.8° C) and F2 (35.7° C). The average values of the humidity varied between 50% and 60%. Variation of the pH showed that the compost went from a slightly acidic phase at the 18th and 21th after incubation to a neutral phase towards the 50th DAI and tended finally stabilized at maturity with pH values of 6.4-6.5. Moreover, GI at T40 days after incubation was significantly higher (p = 0.001, F = 117, 38) for F1 compared with F2, regardless of the associated compost dose. Thus, in (F1) 40 days are enough for GI ≥ 50% whatever the associated compost dose against 50 days for F2. F2 would have more stable organic fractions and would result in longer composting time.